Producing ageing gas for exhaust gas after-treatment systems

ABSTRACT

The invention relates to a process of producing ageing gas for ageing components for the after-treatment of exhaust gas in a burner which comprises a combustion chamber with at least one fuel injection nozzle and with a combustion gas supply system with means for generating swirl, wherein the swirl of the combustion air is set as a function of the selected combustion air ratio λ.

FIELD OF THE INVENTION

The present invention is related to a process for producing ageing gas,and in particular for producing ageing gas for ageing components relatedto an after-treatment of exhaust gas.

BACKGROUND OF THE INVENTION

Motor vehicles with internal combustion engines are subject to emissionlaws which, nowadays, can only be complied with by using exhaust gasafter-treatment systems which adjoin, and are connected to, the internalcombustion engines in the exhaust gas line. The exhaust gasafter-treatment systems have to have the service life which is specifiedby law. For the European Union, after the introduction of exhaust gasstage EURO 4, there is specified a durability in the form of a minimumdriving performance of 100,000 km, whereas after the introduction ofexhaust gas stage EURO 5, a durability in the form of a minimum drivingperformance of 160,000 km has been specified. For homologizing a vehicle(type approval), it is necessary to prove permanent durability of therespective exhaust gas after-treatment systems. For this purpose, thereare permitted artificial ageing processes whose purpose it is tosimulate, in the course of rig testing, wear and damage processes duringthe operation of a motor vehicle in the course of the vehicle servicelife.

For monitoring the durability of exhaust gas after-treatment systemsduring the operation of the vehicle, there are requiredOn-Board-Diagnosis systems (OBD) which, when the exhaust gas limitvalues are exceeded, inform the driver of the faulty operation of theexhaust gas after-treatment systems. Said On-Board-Diagnosis systems arealso tested for their efficiency during a type approval operation usingartificially aged exhaust gas after-treatment systems.

Ageing

The “ageing” of a catalyst refers to the diminishing efficiency of theexhaust gas after-treatment during operation, inter alia as a result ofthe destruction of the catalytically active layer. As a result of thereduction in the size of the active surface it is no longer possible forall emissions to be oxidised and reduced, so that the emissions behindthe catalyst, which are released into the environment, increase. Ageingof the catalysts is substantially caused by two mechanisms which,depending on the point of operation, can occur together or evenseparately. Both mechanisms are also used for specifically ageingcatalysts.

Thermal Aging

Catalysts are designed to operate at temperatures of 200 to 950° C.During this temperature range, the ageing process is very slow. When thetemperature increases to a value in excess of 850° C., the ageingprocess is faster; it is referred to as the so-called thermal ageing, aprocess which intensifies rapidly if temperatures of more than 1000° C.are reached, with the active surfaces being reduced by sinteringprocesses. At temperatures of 1400° C. and more the ceramic membermelts, which leads to total destruction. This is normally indicated by aperformance loss of the engine due to too high an exhaust gas pressurein the catalyst.

Poisoning

There are two types of catalyst poisoning. On the one hand, the activesurface can be poisoned chemically by foreign substances, for examplefuel or oil additives, which chemical poisoning, as a result of chemicalreactions, partially destroys or reduces the catalytic surface. Inaddition, there occurs mechanical poisoning wherein the active layer iscovered for example by lead and sulphur from fuel and oil, which alsoleads to the reduction of the catalytic surface.

OSC Measurements (Oxygen Storage Capacity)

To be able to obtain information on the degree of ageing of a catalyst,it is necessary to make an OSC measurement which serves to determine theoxygen storage capacity of a catalyst from which it is then possible toderive an ageing condition. The older the catalyst, the lower itsstorage capacity. OSC measurements are made in production vehicles andduring artificial catalyst ageing processes.

The OSC measurement is carried out in the steady condition of theexhaust gas temperature and of the mass flow. For this purpose, thelambda signals are measured in front of and behind the catalyst. Theengine or burner is operated in such a way that, within a short time,the exhaust gas abruptly changes from a rich mixture (lambda<1) to alean mixture (lambda>1). The phase displacement between the signal infront of and behind the catalyst (after the change in lambda) isproportional to the oxygen stored in the catalyst.

Artificial Ageing

In the course of the artificial ageing process using an ageing gasproduced in a burner, it is possible to produce endurance and limitcatalysts. In the case endurance catalysts use is made of ageing cycleswhose ageing results are comparable to the catalysts aged in roadtraffic. Measurements to determine the damage to the catalyst to betested are carried out at fixed intervals. These measurements thenenable vehicle manufacturers to develop vehicle-specific catalysts inrespect of structure, coating and service life. If optimum adjustmenthas been achieved, the catalyst can be used. In addition, furtherdynamic cycles like the standard test cycle or the ZDAKW cycle asspecified by law can be used, with air and/or fuel being dynamicallyadded in front of the catalyst for generating an exothermal reaction.

Limit catalysts, on the other hand, are aged until they reach theregionally fixed legal OBD emission limits. These limits are then usedfor establishing a control-technical model for the vehicle, which modelis able to detect if the emission limits have been exceeded. Formeasuring the degree of ageing of the catalysts, the so-called OSCmeasurement is available at the burner test rig, just as it is in thevehicle.

OBD Limit Catalyst Ageing (On Board Diagnosis)

When producing the OBD limit catalyst, the catalysts are aged for acertain period of time at a constant point of operation. For this ageingprocess, use is made of thermal ageing, the purpose of said ageingmethod being to age a catalyst to such an extent that it only justobserves the OBD emission limit. Because, depending on its coating, eachvehicle-specific catalyst behaves in a different way, the length of theageing process cannot be foreseen, which is the reason why the ageingprocess is divided into intervals with subsequent OSC measurements inorder to prevent the catalyst from drifting beyond the limit value andthus cannot be used if the ageing time is too long. In parallel to theOSC measurements, there is carried out an exhaust gas test in order todetermine the emissions of the aged catalyst. For this purpose, thecatalyst is taken from the test rig and built into the associatedvehicle, with the measurement being carried out on a roller test rig inrealistic surroundings (real engine with exhaust gas after-treatmentsystem).

As the oxygen storage capacity and the emissions are connected to oneanother anti-proportionally, but as determining emissions is expensive,the OSC value serves as a measure for the emissions. This means that OBDlimit catalyst ageing is used to determine the OSC value at which theemissions of the vehicle have limit values. At a later stage, in aproduction vehicle, it is then possible with the help of an OSCmeasurement, to detect a defective catalyst and non-observance ofemission values.

ZDAKW Ageing: Cooperation of the German Automotive Industry to Determinethe Further Development of Catalysts

The ZDAKW cycle was developed by the exhaust gas centre of the Germanautomotive industry. It was developed in order to provide a standardtest method for catalyst coatings. Said cycle substantially consists ofa high-temperature phase involving five overrun fuel cut-offs and onepoisoning phase with three temperature levels. When the thrust isdisconnected, the fuel injection is briefly interrupted and, in parallelthereto, the exhaust gas mass flow is reduced. As a result, the catalystis flushed with oxygen and a lambda value of approximately 8 is set.When subsequently intensifying the mass flow and re-starting the fuelinjection, the lambda value is again increased to the set value of 1.The purpose of this process is to simulate the driving operation incases of sudden deceleration and acceleration. During the poisoningphase, at a low temperature level, a somewhat richer mixture of theexhaust gas is guided via the catalyst, the result being that thecatalytically active layer is reduced by chemical poisoning.

State of the Art

It is possible to simulate the process of ageing exhaust gasafter-treatment systems, more particularly exhaust gas catalysts, onengine test rigs, but on the one hand it is expensive and on the otherhand it is difficult to reproduce because engine ageing influencesrepresent an influencing factor which cannot be calculated.

Therefore, there was developed a process and a device according to whichageing gas for aging exhaust gas after-treatment systems is produced inburners in which, depending on the individual case, Otto fuel or dieselfuel is burnt in certain simulation cycles whose purpose it is resemblethe production of exhaust gas during vehicle operation. The respectiveoperating cycles of the burners used must be able to simulate anyinterference like ignition failure and overrun fuel cut-off

From U.S. Pat. No. 7,140,874 B2 there is known a process and a devicefor testing exhaust gas catalysts which contain a burner which, in frontof the combustion chamber, comprises a swirl plate which is providedwith a central through-aperture into which fuel is injected by a fuelinjection nozzle, and with circumferentially distributed boreholesthrough which the combustion air flows into the combustion chamber. Atleast some of said circumferentially boreholes, from the entry end tothe exit end, extend with tangential components and radial components,which leads to a swirl of the combustion air at the entrance to thecombustion chamber.

Producing said swirl plates is expensive, with optimum combustion beingpossible at only one single operating point of the burner, whereas theageing cycles require several operating conditions because the ageinggas has to be provided with different temperatures and, optionally, alsohas to be produced with different combustion air conditions. Moreparticularly, this applies if Otto fuel and diesel fuel is to be used inthe same burner.

SUMMARY OF THE INVENTION

It is therefore the objective of the present invention to provide aprocess and a device which, under stable operating conditions, provideageing gases of different temperatures and which are also suitable forproducing an ageing gas with different combustion air conditions understable burner operating conditions.

Production of Ageing Gas

The objective is achieved by providing a process of producing ageing gasfor ageing components used for the after-treatment of exhaust gas, moreparticularly exhaust gas catalysts, in a burner which comprises acombustion chamber and at least one fuel injection nozzle, as well as asupply pipe for combustion air with means for generating swirl, with theswirl of the combustion air being set as a function of the selectedcombustion air radio By specifically pre-setting the swirl value of thecombustion air, it is possible, in this way, to ensure a stableoperation under different combustion air conditions at different processparameters—depending on the fuel used (Otto fuel or diesel fuel) or inaccordance with the required exhaust gas temperature and/or the requiredexhaust gas composition.

The ageing gas is generated by burning a carbon containing fuel withcombustion air in the burner. The composition of the ageing gas can bemodified by adding additional gas and/or other substances, moreparticularly oil, to achieve as close as possible a similarity withnatural engine exhaust gases. Additional gases can be added in a pureform from storage containers, i.e. gas cylinders. The ageing gas shouldhave a temperature of >250° C., preferably >700° C. and, moreparticularly, 1000 to 1250° C., but optionally also <200° C.

The combustion air ratio can be varied in predetermined cycles inaccordance with the test regulations. In this way, the exhaust gasafter-treatment device can be provided with different ageing gascompositions and ageing gas temperatures in accordance with the loadspectrum such as it corresponds to mixed operational conditions. Byadjusting the parameters of the combustion air ratio as well as fuelquantities and air quantities, the exhaust gas after-treatment devicecan be subjected to cyclical thermal loads and thus experiencesconditions such as they occur under actual driving conditions.

A typical ageing cycle is within a temperature range of 800 to 1250° C.It is also possible to achieve special ageing cycles in which thestarting behaviour of the exhaust gas after-treatment device at the testrig is copied.

A particularly effective way of ensuring a stable burner operation, evenunder dynamic changes in the operating conditions, is achieved if theswirl of the combustion air is varied as a function of the changes inthe combustion air ratio λ in the course of the production of the ageinggas.

It is particularly advisable if the swirl of the combustion air ratio ofλ>1 (lean/stoichiometric) is set to be lower than at a combustion airratio of λ<1 (rich combustion air ratio).

The flow of the combustion air (fresh air) fed into the burner must bemass flow controllable, more particularly by an external combustion airsupply system.

It has been found to be particularly advantageous if the combustion airin an inner primary air flow of the combustion chamber is subjected toswirl and in an outer secondary air flow is supplied in a substantiallyswirl-free condition. More particularly, this applies if the at leastone fuel injection nozzle is arranged centrally in the combustionchamber. An ignition device has to be arranged in the combustion chamberat some distance behind the fuel injection nozzle.

Furthermore, it is advantageous to vary also the supplied combustion airquantity in order to adapt same to the changed quantity of injected fuelwithout allowing excessive effects on the swirl. It is thereforeproposed that the external secondary air flow can be throttled.

The fuel should be injected into the combustion chamber so as to becontrollable in cycles at a high pressure in excess of 20 bar.

According to an advantageous embodiment it is proposed to add ageing gasin an internal return flow in the burner near the at least one fuelinjection nozzle of the combustion air. For this purpose, there has tobe generated a Venturi effect in the central combustion air flow bymeans of which returned ageing gas can be sucked off near the fuelinjection nozzle. This process variant is referred to as primary exhaustgas and ageing gas return.

In order to avoid any disadvantageous effect on the ageing gastemperature, the primary ageing gas return flow is also reduced when thesecondary air flow is throttled.

In order to ensure stable, uniform combustion processes in thecombustion chamber, it is proposed according to a preferred process thatthe axial position of the burner flame is detected for example by meansof a maximum temperature and that, if the burner flame moves towards therear, the swirl of the combustion air is increased and that the swirl ofthe combustion air is reduced when the burner flame moves towards thefront.

When simulating the exhaust gas return such as it occurs in an engine inorder to achieve improved exhaust gas values, it is proposed accordingto a further special type of process that conditioned ageing gas isadded in the combustion chamber to the ageing gas originally produced inthe burner.

To influence the ageing gas temperature to which the exhaust gasafter-treatment systems are subjected, the returned ageing gas can becooled and dried. This process variant is referred to as secondaryexhaust gas return and secondary ageing gas return.

The percentage of the secondary ageing gas return flow of the burner,more particularly, is varied as a function of the required ageing gastemperature. The ageing gas of the secondary ageing gas return flow isadded in the burner preferably in the form of an annular sheath flow.

The conditioned ageing gas can be taken from a main ageing gas pipelinebehind the components for the exhaust gas after-treatment or from abypass ageing gas pipeline which bypasses said components.

According to a further embodiment it is proposed that to the ageing gasproduced in the burner, there is added cold- or hot-conditioned returnedageing gas behind the burner or before entering the exhaust gasafter-treatment components. In this way, too, it is possible toinfluence the temperature of the ageing gas entering the exhaust gasafter-treatment system. The above-described process variant is referredto as tertiary exhaust gas return or ageing gas return.

Oil and/or fuels and/or foreign gas and/or air, such as, age-related,they occur in the course of engine combustion with increasing wear, canbe added in front of the catalyst to the ageing gas of the secondaryand/or tertiary exhaust gas return flow or to the exhaust gas, theadvantage being the reproducibility of said process stages whenproducing the ageing gas as a function of time, i.e. as a function ofthe cycles of the production of ageing gas.

The inventive process is particularly advantageous in that it ispossible to simulate the overrun fuel cut-off of an internal combustionengine in that the fuel supply to the burner is interrupted and that, tore-start the combustion chamber, there is set a combustion air ratio ofλ<1 (rich fuel mixture) in combination of a very high swirl rate of theprimary air flow, which results in very good ignition conditions, sothat the cut-off phases can be observed in a very controlled way. Also,with the objective of reducing the mass flow, exhaust gas can be guidedthrough the catalyst in the bypass. To control the mass flows, it ispossible to use suitable exhaust gas flaps. In addition, it is possibleto age a plurality of catalysts in parallel and to control the massflows by suitable exhaust gas flaps. Furthermore, if exhaust gasmanifolds are provided, the temperature of the individual partial massflows can be set by a measured exhaust gas return and/or by individualexhaust gas flaps.

Ageing Process

The invention comprises a process of ageing components for the exhaustgas after-treatment, more particularly exhaust gas catalysts bysubjecting same to ageing gas which is produced in accordance with theabove-described conditions. Artificial ageing of the entire exhaust gasafter-treatment system takes place in such a way that hot ageing gaswith C-, HC- and/or NOx-containing components is produced in a burnerand guided through the exhaust gas after-treatment system, wherein thehot ageing gas subjects the exhaust gas after-treatment components forthe after-treatment of C-, HC- and/or NOx-containing components to thesame loads in the same way as engine exhaust gas naturally producedunder actual driving conditions.

Burner

Furthermore, the invention comprises a burner for producing ageing gasfor the ageing of components for the after-treatment of exhaust gas,more particularly exhaust gas catalysts, which burner comprises acombustion chamber with a combustion chamber axis and at least one fuelinjection nozzle and a combustion air supply line which comprises swirlgenerating means which are adjustable in the sense of changing the swirlintensity of the combustion air. Said swirl generating means can beadjusted from the outside without having to remove the burner in orderto preset the swirl intensity or adjust the swirl intensity duringoperation. Said adjustment can take place in accordance withpre-programmed combustion cycles and/or within the framework of controlprocesses.

More particularly, the swirl generating means of the combustion airsupply line are circumferentially distributed swirl blades which arearranged radially relative to the combustion chamber axis and which arepivotable on journals. They preferably engage one single rotatableadjusting ring which cooperates with the swirl blades.

According to a preferred embodiment there is provided an annular plateor funnel which is arranged in the combustion air supply flow in frontof the fuel injection nozzle and which divides the combustion air flowinto an inner primary air flow and an outer secondary air flow, with theswirl generating means preferably being positioned in the primary airflow. More particularly, it is the combustion air flow positioned nearthe fuel injection nozzle which has to be provided with a variableswirl, whereas the outer secondary air flow which optionally constitutesa greater volume flow percentage remains substantially swirl-free.

However, it is proposed furthermore that there are provided means forcontrolling the volume of the combustion air flow, which means, moreparticularly, can act on the outer secondary air flow. The means forcontrolling the volume flow of the combustion air flow are provided inthe form of a ring which is arranged concentrically relative to the fuelinjection nozzle and which comprises adjustable apertured diaphragms.

For detecting the axial position of the burner flame inside thecombustion chamber there can be provided one or more special sensors,more particularly temperature sensors which are arranged so as to bedistributed along the length of the combustion chamber.

Further design characteristics consists in that inside the combustionchamber there is concentrically arranged a flame pipe which ends infront of the end of the combustion chamber and which, near the fuelinjection nozzle, comprises circumferentially distributed exit aperturesfor returning primary ageing gas. To ensure that the latter is guidedinto an independent return flow, it is proposed that the exit aperturesin the flame pipe are positioned in a flame pipe portion which isnarrowed nozzle-like and arranged behind the fuel injection nozzle, witha Venturi effect occurring in the primary combustion air flow.

A further advantageous embodiment consists in that inside the burnersheath, there is provided a mixing pipe which is arranged concentricallyrelative to the combustion chamber axis, which, together with the burnersheath, forms an annular chamber to which there is connected a supplyport for conditioned returning ageing gas and which extends beyond thelength of the flame pipe and, behind the end of the flame pipe,comprises circumferentially distributed exit apertures for theconditioned ageing gas. This embodiment, more particularly, serves foradding secondary returned conditioned ageing gas as described above inconnection with the various processes.

System Suitable for Ageing Purposes

The invention comprises a system for artificially ageing exhaust gascatalysts and exhaust gas after-treatment systems which are subjected toageing gas produced in a burner, into which system there is inserted aburner according to one of the previously mentioned embodiments.

System Components

Such a system consist of the following components: air supply line, fuelsupply line, burner with mixing device, ageing pipeline for the exhaustgas after-treatment components to be aged and an ageing gas return line.

Air Supply

The air supply line is used to supply the burner with combustion air forthe purpose of producing, together with the fuel, an ignitable mixtureat a later stage. Fresh air is sucked in via an air filter, which freshair is compressed via a Roots compressor which is driven by anasynchronous motor. As a result of the pressure gradient relative to theambient air at the exhaust gas chimney behind the exhaust gasafter-treatment system, there occurs a mass flow in said direction. Theasynchronous motor is speed-controlled via a frequency converter.Subsequently, the temperature of the compressed combustion air can becooled down via a counter flow heat exchanger. Behind the fresh air haspassed through the air filter, a hot film air mass sensor (HFM) measuresthe mass flow which is controlled via a subsequently arranged throttlevalve. The quickly controlling throttle valve is essential because theRoot compressor is too inert for achieving the rapid mass flowvariations required for the various cycles. In this way, the combustionair reaches the burner head with a certain mass flow and a certaintemperature.

Fuel Supply

By means of a fuel pump, the fuel is pumped from a tank into the burner.A mass flow meter measures the fuel through-put. A counter flow heatexchanger cools the fuel which is not required. A high-pressure pump nowincreases the fuel pressure to 50 bar which is required for theinjection valve.

Burner with Mixing Device

At the entry end, an entry manifold, also referred to as the burnerhead, forms the transition from the cold to the hot part of the system.At the exit end, the combustion chamber forms the transition to theexhaust gas after-treatment system via a flange.

For cooling the components in the mixing device, the two-shell entrymanifold is cooled by cooling water sheath.

The mixing device substantially consists of the following components:air controlling unit with swirl device and diaphragm, injection nozzlewith injection valve and flame pipe.

It is the purpose of the mixing device to mix the fuel and thecombustion air in such a way as to produce a combustible mixture whichis burnt in the flame pipe in order to provide, at the burner exit, anexhaust gas mixture which resembles the exhaust gases of an Otto engineor diesel engine.

After the exhaust gas has left the flame pipe, it is gradually cooleddown by adding the cooled conditioned ageing gas of the secondaryexhaust gas recirculation flow (EGR). By supplying the ageing gaslaterally, a swirl flow occurs around the mixing pipe. Rebound platesand boreholes ensure that the colder returned ageing gas is pressed intothe inside of the combustion chamber, so that, towards the rear, thereis generated an ageing gas with an ever decreasing temperature. Theexhaust gas temperature at the burner exit can additionally beinfluenced by adding specific amounts of air, with the mass flow whichsubsequently flows through the exhaust gas after-treatment systemconsisting of a fresh air mass flow, an EGR mass flow and a fuel massflow.

By measuring the temperature in several places of the combustionchamber, it is possible to detect the position of the flame and to setthe position of the flame by varying the swirl.

Ageing Path

Ageing takes place between two flange connections. The first flangeconnection is directly behind the burner exit whereas the second flangeconnection is located in front of a particle filter. The flanges arearranged at a constant distance from one another, so that the catalyststo be treated can be adapted to the system in advance. As the geometryand exhaust gas line of the catalysts to be aged usually greatly differfrom one another, said adaptation measures always have to be undertakenindividually. As a rule, every catalyst is provided with connectingmuffs in front of and behind the catalysts for lambda probes and withseveral threaded muffs for thermo elements and temperature sensors.Depending on the ageing capacity of the burner and the ageing gasrequirements for the catalysts, two or more catalysts can be connectedin parallel in the ageing path. For controlling the mass flow, at leastone bypass line leading to the catalysts can be provided in the ageingpath. Ageing gas return

The returning ageing gas flow removes part of the exhaust gas mass flowin front of the exhaust gas chimney to mix same again in a cooledcondition with the original ageing gas. For this purpose, the hot ageinggas is guided over a counter flow heat exchanger which cools same downto 40° C. The cooled ageing gas is guided over a cyclone separator forthe purpose of filtering out the liquid phase after the cooling process.Now the mass flow of the returned ageing gas is determined via a hotfilm air mass sensor (HEM), to be able to control same via an adjoiningthrottle valve and a Roots compressor, Finally, the cooled ageing gasreaches the burner where, via the mixing pipe, it is added to the hot,originally produced ageing gas.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of an inventive burner and of an inventive systemfor artificially ageing exhaust gas catalysts are illustrated in thedrawings and will be described below.

FIG. 1 is an inclined view of a complete inventive burner with a partialsection.

FIG. 2 is an inclined view of part of the burner with the combustionchamber according to FIG. 1 with a partial section.

FIG. 3 is an inclined view of the front region of the burner accordingto FIGS. 1 and 2 with an air supply arch with a partial section.

FIG. 4 shows the mechanical part of the air supply system as well as thebeginning of the flame pipe according to FIGS. 1 to 3 in a longitudinalsection.

FIG. 5 shows the design principles of an inventive system forartificially ageing exhaust gas catalysts.

FIG. 6 shows an embodiment of an inventive system for artificiallyageing exhaust gas catalysts in a side view.

FIG. 7 is a diagram of OSC measurements made at a catalyst.

FIG. 8 is a diagram of the ZDAKW catalyst ageing cycle.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

FIG. 1 shows an inventive burner 10 with a combustion chamber 11, whichburner 10 comprises an outer rotationally symmetric burner sheath 12which extends between an entry flange 1 and an exit flange 14 andcomprises three length portions 16, 17, 18 whose diameter decreases fromthe entry flange to the exit flange and which are connected to oneanother via conical transition portions 19, 20. A carrier flange 15which comprises an outer collar and an inner annular projection to bedescribed in greater detail with reference to the following Figures isthreaded to the entry flange 13. The collar centres the entry flange 13to which there is attached the burner sheath 12. On its outside, theinner annular projection at the carrier flange 15 carries a mixing pipe21 for returning conditioned ageing gas and extends, at a radialdistance, along the length of the first two portions 16, 17 of theburner sheath 12 and of the two conical transition portions 19, 20. Fromthe transition portion 19 to the transition portion 20, with bothportions being included, the mixing pipe 21 comprises substantiallyuniformly distributed inlet apertures 22.

The inner annular projection at the carrier flange 15 carries acylindrical flame pipe 23 which, in respect of length, substantiallyextends along the first portion 16 of greatest diameter of the burnersheath 12. Inside the flame pipe 23 there are provided two rows ofrecirculation apertures 24 for a primary ageing gas circulation whichwill be explained at a later stage.

An ageing gas return pipe (port) 26 which, at a short distance behindthe entry flange 13, ends in an annular chamber 27 between the burnersheath 12 and the additional guiding pipe 21, is attached to the burnersheath 12. Said ageing gas return pipe 26 serves to return the secondaryageing gas.

At the entry end in front of the flame pipe 23, there is connected amixing device 25 with a fuel injection nozzle 31 and a air controllingdevice 32. The air controlling device 32 comprises an adjustable swirldevice and an adjustable throttle diaphragm for the combustion air,which two devices will be explained at a later stage. In front of theburner 10 there is provided an air supply manifold 34 which is connectedthereto by an attaching flange 33 and which comprises an inner jacket 35and an outer jacket 36 between which there is formed a shell-typechamber 38 for cooling water. In addition to the attaching flange 33,the air supply manifold 34 comprises an entry flange (not shown here).Further details of the parts mentioned latterly are given in thefollowing Figures.

The principle used for carrying out the combustion process correspondsto that of a burner stabilised by swirl. From behind, the fresh airflows out of the cooled air supply manifold 34 into the mixing device 25where the air flow is divided into an inner primary air flow and anouter secondary air supply. In the case of the primary air flow, thefresh air, on the inside, flows over the swirl device. Then, in front ofthe primary air supply borehole in the throttle diaphragm, the fresh airis mixed with the injected fuel, and the combustible fuel-air mixturereaches the flame pipe 23. In the case of the secondary air flow, thefresh air is guided around the swirl device and, via secondary airboreholes in the throttle diaphragm, flows into the flame pipe andenvelops the fuel-air mixture, so that, during the combustion process,the edge regions, too, are supplied with oxygen and so that part of theageing gas generated in the course of combustion is sucked back via therecirculation bores 24 in the flame pipe 23. By changing the aperturecross-section of the secondary air boreholes in the throttle diaphragm,it is possible, to variably and divisibly control the air quantitythrough the swirl device (primary air borehole) and around same(secondary air boreholes). As a result, the air flow speed at the exitof the mixing device 25 is changed, so that there occurs a vacuum at therecirculation boreholes 24 of the flame pipe 23. The recirculationboreholes 24 serve to stabilise the flame, and via the air circulationboreholes 24 ageing gas on the outside of the flame pipe 23 is sucked up(Venturi effect). In consequence, the ageing gas deposits itself fromthe outside like a jacket around the flame.

In FIG. 2, any details identical to those shown in FIG. 1 have beengiven the same reference numbers. To that extent, reference is made tothe description above. In FIG. 2, the collar 28 and the annularprojection 29 at the carrier flange 15 are mentioned for the first time.On the collar 28, the flange 13 is fixed with the mixing pipe 21. In theannular projection 29, there is contained an inserted carrier ring 30which carries the air controlling device 32 as well as the fuelinjection nozzle 31. FIG. 2 shows further details of the burner, i.e.swirl blades 41 between the burner sheath 12 and the mixing pipe 21 aswell as an ignition device 45 with two electrodes 46, 47. In the airsupply manifold 34 there can be seen a further through-sleeve 48 forattaching the ignition device 45. Furthermore, it can be seen that theflame pipe 23 comprises a nozzle-like necking 42 near the aircontrolling device 32, in which there are provided circumferentiallydistributed gas supply apertures 43 through which the primary quantityof recirculation gas is sucked up. Via a pipeline (not shown), thecentral fuel injection nozzle 31 is supplied with fuel and, through athrough-sleeve 39 in the air supply manifold 34, enters the latter. Aninner shaft 65 for adjusting the swirl device and a coaxially extendinghollow shaft 68 for adjusting the throttle diaphragm enter the airsupply manifold 34 through a further through-sleeve 40.

Details of the air controlling device 32 and its adjusting mechanismwill be described with reference to the following Figures.

In FIG. 3, any details identical to those shown in the previous Figureshave been given the same reference numbers. To that extent, reference ismade to the description above. It can be seen that the carrier ring 30in the annular projection 29 is connected to the flame pipe 23 in thesame way as to the air controlling device 32. The carrier ring 30comprises a first annular disc 51 with a plurality of airthrough-apertures 52 and a central aperture for receiving the fuelinjection nozzle 31. In the direction of flow behind the annular disc 51there is positioned a rotatable annular disc 53 as well as a fixedannular disc 54. The two annular discs 53, 54 are separated from oneanother by an insulating disc 57. The annular discs, together, form athrottle diaphragm. They each comprise a central aperture 55 for theprimary air and a ring of apertured diaphragms 56 for the secondary air.By adjusting means not shown here, the annular disc 53 is rotatablerelative to the annular disc 54, so that the apertured diaphragms 56 inthe annular disc 54 can be throttled and, respectively, reduced in theirthrough-cross-section.

Between the two annular discs 51 and 52, there extends an initiallycylindrical and then funnel-shaped annular sheath 61 which separates aninner primary combustion air flow ring from an outer secondarycombustion air flow ring. Inside the annular sheath 61 and thus insidethe inner primary combustion air flow ring there are positionedcircumferentially distributed, adjustable swirl flaps 62 on radiallyarranged rotary journals 63 through which the inner primary combustionair flow ring can be influenced in respect of swirl, whereas the outersecondary combustion air flow ring can be adjusted by the adjustableapertured diaphragms 56 in respect of the volume flow quantity.

In FIG. 4, any details identical to those shown in the previous Figureshave been given the same reference numbers. To that extent, reference ismade to the description above. FIG. 4 shows an adjusting device 64 whichis supported in the through-sleeve 40 and in the first annular disc 51and which comprises a rotatable inner shaft 65 which, via a pinion 66acts on an outer annular gear 67 at the second annular disc 53 and whichcomprises a rotatable hollow shaft 68 which, via a pinion 69, acts on asetting ring 70 for rotating the swirl flaps 62. At the setting ring 70,there are arranged driving journals 60 which act on the throttle flaps62 which are pivotable on rotary journals 63. FIG. 5 shows the designprinciples of a system for aging exhaust gas catalysts, which system, asthe central component, comprises a burner 10 according to the invention.The system comprises part of a fuel supply unit 71 and parts of acombustion air supply unit 81.

At the fuel supply unit 71 it is possible to identify a fuel tank 72, afuel conveying pump 73 as well as a low-pressure fuel pump 74 and ahigh-pressure fuel pump 75 with an electric motor. A mass flow sensor 76is arranged behind the low pressure fuel pump 74. A return loopextending parallel to the low-pressure fuel pump comprises a pressureregulating valve 77 and a fuel re-cooling device 78. The returning loopextending parallel to the high-pressure pump 75 comprises a pressureregulating valve 79 and a fuel re-cooling device 80.

At the combustion air supply line 81 it is possible to see an air filter82 and a mass flow sensor 83 which are followed by a throttle flap 84and a Roots compressor 85 with a frequency-controlled electric motor.Behind the compressor 85 there is positioned a charge air cooler 86 infront of the entrance to the burner 10.

When fuel and combustion air are supplied by the means 71, 81 asmentioned, the burner 10, when ignited by an ignition device, producesageing gas which can pass through exhaust gas catalysts 91, 92 and adiesel particle filter 95, and the exhaust gas catalysts, for example,can be TWC- or DOC- or SCR- or CDPF-catalysts and can be arrangedparallel relative to one another.

The main ageing line 100 is divided into two ageing gas branch lines115, 116 leading to the exhaust gas catalysts 91, 92 and a centrallypositioned ageing gas bypass line 119. The branch lines contain settingvalves 93, 94 in front of the catalysts 91, 92 and setting valves 117,118 behind the catalysts in which the mass flows can be divided, i.e.set so as to be of equal size. In the bypass line 114, there is provideda metering valve 120 and a switching valve 121 which can be used tocontrol the size of the bypass flow and thus the mass flows leading tothe catalysts. The branch lines 115, 116 and the bypass line 119 arecombined again to form the main ageing gas line 100 in front of thetheses particle filter 95. The controllable burner 10 is used to runthrough certain operating cycles which serve to effect standard ageingof the exhaust gas catalysts 91, 92 and optionally of the dieselparticle filter 95.

The line diagram can be used analogously for treating further parallelcatalysts.

The main flow of the after-treated ageing gas is discharged from themain ageing gas line 100 via an exhaust gas chimney 101, while a partialflow, via a secondary return line 98, returns secondary ageing gasafter-treated as exhaust gas to the burner 10. Optionally, via asecondary ageing gas bypass line 114, ageing gas can be branched offbehind the burner 10 and in front of the exhaust gas after-treatmentsystem and returned in the form of secondary ageing gas to the burner.At the entry to the return line 98, there is arranged a regulating valve122 for the exhaust gas after-treated ageing gas, and in the return line114, there is positioned a regulating valve 124 for thenon-after-treated ageing gas by means of which the composition of thesecondary ageing gas can be varied. In the return line 98 for thesecondary ageing gas, there is arranged an exhaust gas heat exchanger102 as well as a condensate separator 103 with a controllable outletvalve 104. The condensate separator 103 is followed by a mass flowsensor 105 which, in turn, is followed by a throttle flap 106 and aRoots compressor 107 which is driven by a frequency-controlled electricmotor.

In front of the return line 98, before same enters the burner 10, therebranches off a return branch line 99 which, behind the burner, ends inthe main ageing gas line 100; the point of entry is connected to a mixer96 and can serve for returning the so-called tertiary ageing gas. In thereturn branch line 99, there is arranged a controllable shut-off valve109. A mixer 108 can be used for adding to the tertiary ageing gas aliquid such as oil or fuel or foreign gases for each of which there areprovided branch lines 112, 113 leading to the mixer 108 withcontrollable inlet valves 110, 111. In front of the return branch line99 there branches off an ageing bypass line 123 which, in the bypassleading to the main ageing gas line, bypasses the mixer 96 and isdivided into two branch lines 125, 126 for cooled and conditioned ageinggas, which each lead into ageing gas branch lines 115, 116 leading tothe exhaust gas catalysts 91, 92. Into each of the branch lines 125, 125there are inserted regulating valves 127, 128 which are used formeasuring the added cooled ageing gas and by means of which the ageinggas temperature in the exhaust gas catalysts can be influenced, moreparticularly lowered.

FIG. 6 is a side view of a complete system, which is simplified ascompared to the diagrammatic view of the system shown in FIG. 5.

There can be seen a burner 10 which is enveloped by an insulating jacket50 and which is followed by and connected to two exhaust gas catalysts91′, 92′ connected in series, as well as a diesel particle filter 95.The main ageing gas line 100 ends in an exhaust gas chimney 101. Fromsaid main line there branches off a return line 98 in which there isarranged an ageing gas re-cooling device 102 which is followed by acondensate separator 103 with an outlet valve 104, which, in turn, isfollowed, in the return line 98, by a mass flow sensor 105 and athrottle flap 106. Behind the throttle flap 106, in the line 98, therecan be seen a Roots compressor 107 which can be driven by afrequency-controlled electric motor. Following the Roots compressor, thereturn line 98 laterally ends in the burner 10 in the starting region ofthe combustion chamber. While the fuel supply system is not shown inthis Figure, it is possible, of the air supply system 81, to see the airfilter 83, the throttle flap 84, the Roots compressor 85 drivable by afrequency-controlled electric motor and the charge air cooler 86.

FIG. 7 shows the diagram of an example of an OSC measurement of lambdavalues as a function of time, measured by a lambda probe which is fittedin front of the catalyst and whose measuring signal is referred to as“lambda before cat”, and by a lambda probe which is fitted behind thecatalyst and whose measuring signal is referred to as “lambda aftercat”. To be able to provide information on the degree of ageing of acatalyst, there is carried out an OSC measurement which serves todetermine the oxygen storage capacity of a catalyst, from which theageing condition can be derived. The OSC measurement is used inproduction vehicles and for measuring artificial catalyst ageing.

The OSC measurements are carried out in the steady condition of theexhaust gas temperature and in mass flows. For this purpose, lambdasignals are measured in front of and behind the catalyst. The burner isnow supplied with fuel in such a way that, within a short time, theexhaust gas abruptly changes from a fatty mixture (lambda<1) to a leanmixture (lambda>1), with the curve aimed at being represented by thecurve “Nominal lambda”. The phase displacement between thebefore-catalyst signal “lambda before cat” and the after-catalyst signal“lambda after cat” is proportional to the oxygen stored in the catalyst.FIG. 7 shows such a measurement taken at the catalyst ageing test rig.

The catalyst measured here still has a high oxygen storage capacity. Itcan clearly be seen that the lambda value after the catalyst (lambdaafter cat) increases more slowly than the lambda signal before thecatalyst (lambda before cat) and only seconds later reaches its maximumvalue. A limit catalyst, on the other hand, shows a different behaviour.Shortly after the maximum value of the lambda signal of the sensor infront of the catalyst has been reached, the lambda value at the sensorbehind the catalyst would reach maximum values. Both lambda signalswould increase nearly simultaneously.

FIG. 8 shows the diagram of the ZDAKW cycle which was developed by theExhaust Gas Centre of the German Automotive Industry (ADA). It shows thenominal temperature T-nominal as a function of time, with the nominalvalue of the combustion air ratio λ-soll equalling 1, with the exceptionof the phases of the overrun fuel cut-off in which the combustion airratio λ is set so as to be greater than/equal to 8. This cycle issubstantially composed of a high temperature phase with five thrustdisconnections and a poisoning phase with three temperature levels. Inthe case of an overrun fuel cut-off, the fuel injection is brieflyinterrupted and reduced in parallel to the exhaust gas mass flow return.As a result, the catalyst is flushed with oxygen, with the lambda valueof greater than/equal to 8 being set. When subsequently starting up andincreasing the exhaust gas mass flow return and re-introducing fuelinjection, the lambda value increases to the set value of λ=1. Thisprocess is to simulate driving with sudden deceleration andacceleration. During the poisoning phase, at a low temperature level, aslightly richer mixture of the exhaust gas is guided over the catalyst,the result being that the catalytically active layer is reduced due tochemical poisoning.

The high temperature phase of a duration of 600 seconds is passedthrough 48 times. The poisoning phase of a duration of 30 minutes ispassed through 8 times. The entire cycle lasts 96 hours. The completecycle corresponds to a driven distance of 80,000 km.

It is to be understood that various modifications are readily made tothe embodiments of the present invention described herein withoutdeparting from the scope and spirit thereof. In addition, Accordingly,it is to be understood that the invention is not limited by the specificillustrated embodiments, but by the scope of appended claims.

1. A process of producing ageing gas for ageing components for theafter-treatment of exhaust gas in a burner, the process comprising: acombustion chamber with at least one fuel injection nozzle and with acombustion gas supply system that can generate a swirl, characterised inthat the swirl of the combustion air is set as a function of theselected combustion air ratio λ.
 2. The process according to claim 1,characterised in that the swirl of the combustion air is changed as afunction of changes in the combustion air ratio λ during the productionof ageing gas.
 3. The process according to claim 1, characterised inthat, with a combustion air ratio of λ22 1 (lean/stoichiometric), theswirl of the combustion air is set to be lower and is set to be higherwith a combustion air ratio of λ<1 (rich).
 4. The process according toclaim 1, characterised in that the entire flow of the combustion air canbe mass flow controlled.
 5. The process according to claim 1,characterised in that the combustion air is divided into an innerprimary air flow and an outer secondary air flow, wherein the combustionair in the inner primary air flow is supplied with a swirl.
 6. Theprocess according to claim 5, characterised in that the combustion airin the outer secondary air flow is supplied in a substantiallyswirl-free condition.
 7. The process according to claim 1, characterisedin that the secondary air flow can be throttled, wherein the secondaryair flow is throttled more particularly for achieving a combustion airratio of λ<1 (rich).
 8. The process according to claim 1 characterisedin that an axial position of the burner flame inside the combustionchamber is detected and that, with the burner flame having moved to therear, the swirl of the combustion air is increased and reduced when theburner flame has moved to the front.
 9. The process according to claim1, characterised in that ageing gas is returned from the combustionchamber in the form of a sheath flow into the region of the fuelinjection nozzle (primary ageing gas return).
 10. The process accordingto claim 9, characterised in that, when the secondary air flow isthrottled, the primary ageing gas return flow is also reduced.
 11. Theprocess according to claim 1, characterised in that to the ageing gasoriginally produced in the burner there is added conditioned ageing gasin the combustion chamber treatment and provides a secondary ageing gasreturn flow.
 12. The process according to claim 11, characterised inthat the percentage of the conditioned ageing gas of the secondaryageing gas return flow is modified for the purpose of maintaining apredetermined ageing gas temperature.
 13. The process according to claim11, characterised in that the conditioned ageing gas of the secondaryageing gas return flow in the burner is added in the form of an annularsheath flow.
 14. The process according to claim I characterised in that,for re-starting the combustion chamber, in order to simulate an overrunfuel cut-off, there is set a combustion air ratio λ<1 (rich) and a highdegree of swirl of the primary air.
 15. The process according to claim1, characterised in that, behind the burner and in front of thecomponents for the after-treatment of exhaust gas, conditioned ageinggas is added to the ageing gas produced in the burner and provides atertiary ageing gas return flow.
 16. The process according to claim 15,characterised in that oil and/or fuel and/or foreign gas and/or air isadded to the conditioned ageing gas of the tertiary ageing gas returnflow.
 17. The process according to claim 1 characterised in that thefuel injection is controlled in cycles with a pre-pressure of at least20 bar.
 18. The process of ageing components for the after-treatment ofexhaust gas by subjecting same to ageing gas, characterised in that theageing gas for treating the components for the after-treatment ofexhaust gas is produced in accordance with claim
 1. 19. A burner forproducing ageing gas for ageing components used for the after-treatmentof exhaust gas, said burner comprising: a combustion chamber with acombustion chamber axis, at least one fuel injection nozzle and acombustion air supply line which is provided with means for generatingswirl, characterised in that the means for generating swirl areadjustable in the sense of changing the swirl intensity.
 20. The burneraccording to claim 19, characterised in that an annular sheath or funnel(61) in the combustion air flow is positioned in front of the fuelinjection nozzle (31), which sheath or funnel (61) divides thecombustion air flow into an inner primary air flow and an outersecondary air flow, wherein swirl is generated in the primary air flow.21. The burner according to claim 20, characterised in that the swirl isgenerated only in the primary air flow.
 22. The burner according toclaim 19, characterised in that the swirl generating means comprisecircumferentially distributed pivotable swirl blades (62) positioned onaxes arranged radially relative to the combustion chamber axis.
 23. Theburner according to claim 19, characterised in that in the burner thereare provided means for controlling the volume flow of the combustion airflow.
 24. The burner according to claim 23, characterised in that themeans for controlling the volume flow of the combustion air flow arearranged annularly in the secondary air flow.
 25. The burner accordingto claim 23, characterised in that the means for controlling the volumeof the combustion air flow comprise of a ring of adjustable apertureddiaphragms (56), which ring is arranged concentrically relative to thefuel injection nozzle.
 26. The burner according to claim 19,characterised in that there are arranged means for detecting the axialposition of the flame in the combustion chamber (11), more particularlyone temperature sensor or a plurality of temperature sensors arrangedalong the length of the combustion chamber.
 27. The burner according toclaim 19, characterised in that, in the combustion chamber (11), thereis provided a concentrically arranged flame pipe (23) which ends infront of the combustion chamber (11) and which, near the fuel injectionnozzle (31), comprises circumferentially distributed apertures (43) forthe returning ageing gas of the primary ageing gas return flow.
 28. Theburner according to claim 27, characterised in that the exit apertures(43) in the flame pipe (23) are positioned in a portion (42) of theflame pipe (23), which portion (42) is narrowed like a nozzle.
 29. Theburner according to claim 19, characterised in that inside the burnersheath (12), there is positioned a mixing pipe (21) which is arrangedconcentrically relative to the combustion chamber axis and which,together with the burner sheath (12), forms an annular chamber (27) towhich there is connected a supply port (26) for conditioned ageing gas,wherein the mixing pipe (21) extends beyond the length of the flame pipe(23) and, behind the end of the flame pipe (23), comprisescircumferentially distributed exit apertures (22) for the conditionedageing gas of the secondary ageing gas return flow.
 30. The burneraccording to claim 19, characterised in that the fuel injection nozzle(31) is supplied by a high-pressure injection valve which can becontrolled in cycles.
 31. The burner according to claim 30,characterised in that the fuel injection nozzle (31) is combined withthe high-pressure injection valve to form a unit and is arranged insidethe swirl generating means.
 32. A system for ageing components for theafter-treatment of exhaust gas by subjecting said components to anageing gas produced in a burner, characterised in that there is provideda burner (11) according to claim 16 to which the components for theafter-treatment of exhaust gas are connected via an ageing gas pipeline(100).
 33. The system according to claim 32, characterised in that thesupply port (26) is connected to a pipeline (98) for ageing gas which isproduced in the burner (10) and subsequently conditioned.
 34. The systemaccording to claim 33, characterised in that, in the pipeline (98),there is arranged an ageing gas recooling device (102).
 35. The systemaccording to claim 33, characterised in that, in the pipeline (98),there is arranged a throttle flap (106) and a controllably drivencompressor (107).
 36. The system according to claim 33 characterised inthat that the pipeline (98) is connected to a main ageing gas pipeline(100) behind the components for the after-treatment of exhaust gas or toan ageing gas bypass pipeline (114) in the bypass leading to thecomponents for the after-treatment of exhaust gas.
 37. The systemaccording to claim 33, characterised in that prior to the pipeline (98)for conditioned ageing gas being connected to the supply port (26), abranch pipeline (99) is branched off said pipeline (98) and ends behindthe burner (10) in the main ageing gas pipeline (100).
 38. The systemaccording to claim 37, characterised in that feeding pipelines (112,113) for oil and/or fuel and/or foreign gas and/or air end in the branchline (99).